The present invention relates to a chip-type light-emitting device with case. More specifically, the present invention relates to a chip-type light-emitting device with case, in which an LED chip is bonded onto a substrate formed with electrodes on its surface, and the LED chip on the substrate is surrounded by a case having an inner wall of a hole shaped like a frustum of a cone, and a transparent resin is filled in the inner wall as a sealant.
One example of such a kind of chip-type light-emitting device with case is disclosed in, for example, Japanese Patent Laying-open No. 11-2207178 [H01L 33/00] laid-open on Aug. 10, 1999. As shown in FIG. 4, this semiconductor light-emitting device 1 includes a second white substrate 2, and an LED element 3 is stored in a concave portion 2a formed on the white substrate 2. In addition, the LED element 3 is die-bonded onto a first white substrate 4. Furthermore, the LED element 3 is entirely covered and sealed by a light-transmissible synthetic resin molding portion 5 filled in the concave portion 2a. In the semiconductor light-emitting device 1, a light-emitting efficiency was improved by emitting a light to a light-emitting surface by reflecting it on the first white substrate 4 and the second white substrate 2, even if the light is outputted from the LED element 3 to a side surface direction and a bottom surface direction opposite to the light-emitting surface.
However, in this prior art, although the light is reflected by the first white substrate 4 and the second white substrate 2, none is given any consideration as to an inner surface form and the like of the concave 2a, a reflection efficiency was thus not sufficiently improved. In other words, the light-emitting efficiency was still not sufficient.
Therefore, a primary object of the present invention is to provide a chip-type light-emitting device with case capable of improving a light-emitting efficiency.
The present invention is a chip-type light-emitting device with case, in which an LED chip is bonded onto a substrate formed with electrodes on its surface, and the LED chip on the substrate is surrounded by a case having an inner wall of a hole shaped like a frustum of a cone tapering downward, and a resin which functions as a sealant is filled in the inner wall of the case characterized in that a light outputted from the LED chip is entirely reflected by an inner surface of the sealant by forming a gap between the inner wall and the sealant.
In the chip-type light-emitting device with case, electrodes are formed on a top surface of the substrate, and the LED chip is bonded onto the electrodes. Furthermore, a case having an inner wall of a hole shaped like a frustum of a cone tapering downward surrounds the LED chip, in which a transparent resin as a sealant is filled. When the transparent resin is cured, the transparent resin itself hardens and shrinks, and therefore, a gap is formed between the inner wall and the transparent resin (sealant). In the chip-type light-emitting device with case, since a light outputted from the LED chip is reflected entirely on the inner surface of the sealant, it is possible to efficiently reflect the light outputted from the LED chip.
For example, an impregnation prevention layer is formed on the inner wall of the case, it is thus possible to prevent the transparent resin from impregnating in the case. Due to this, the sealant becomes easily separated from the case at a time the sealant hardens and shrinks. It is thus possible to surely form the gap.
As for the impregnation prevention layer, a relatively thick nickel layer (for example, 5-10 xcexcm) is used. By forming the nickel layer thickly, a degree of smoothness of the inner wall of the case can be increased, it thus becomes possible to make an outer surface (inner surface) of the sealant even, and therefore, it results in an improved reflection efficiency on the inner surface of the sealant.
The nickel layer is formed on copper or silicon layer by plating.
According to the present invention, the light outputted from the LED chip is entirely reflected on the inner surface of the sealant, it is thus possible to reflect the light efficiently. Therefore, it is possible to improve the light-emitting efficiency.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.